This invention generally relates to the field of voice and data services and in particular to a method and an apparatus for switching a telephone receiver between voice and data modes.
Analog display services interface (ADSI) enables alternate voice and data capability over existing analog telephone networks. ADSI is a telecommunications protocol standard developed by Bell Core and published in Bell Communications Research Report "Generic Requirements for and SPCS to Customer Premises Equipment Data Interface for analog display services," Technical Reference TR-NWT-001273, December, 1992 (incorporated herein by reference). This capability permits ADSI devices to communicate with users through a familiar voice response audio interface, where the user listens to voice recordings and makes menu selections using the telephone keypad, and with visual menus and information on a screen display, where service selections can be made using softkeys. Currently, ADSI devices are often implemented as screen-display telephone terminals, but there can also be television set-top boxes allowing users to make calls using the television, personal digital assistants (PDAs), pagers, and personal computers that are ADSI capable.
In addition to real-time interactive applications, ADSI also enables program transfer using a capability known as Feature Download. These programs, or service scripts, can be developed by a server and run on a local terminal. In many cases, these scripts are created by an authoring tool and stored in an external database for access by the telephony platform serving the user. Therefore, when new features are requested by the user, or are newly added by the server, the scripts are transferred by the telephony platform to the ADSI terminal where they are stored in memory and executed by the terminal until overwritten. These scripts define not only call flow, but also define the softkeys and displays presented to the user during a call.
One example of applied ADSI technology is Northern Telecom's Advanced Call Management Service (ACMS). In ACMS, customer selected features are stored in an external database. When a customer calls in for activation of services, a database lookup is performed so that the appropriate information for that customer can be downloaded to the telephone. The application runs on a computer telephony platform such as a Network Applications Vehicle (NAV), which is typically a UNIX-based telephony platform, and which reads an object file to get information concerning the call flow. The NAV presents the call flow, including ADSI commands, to the end user and as a result a new application is presented to the terminal.
In addition, any server may create Custom Local Area Signaling Services (CLASS).SM. or Custom Calling Features (CCF) and download these advanced feature download scripts that are specifically tailored to the user's service subscription. As a result, a user can activate services such as three-way calling, call waiting, and call forwarding through context sensitive screen prompts and softkeys. These advanced call management telephony script applications have been a primary area of development for ADSI display terminals.
The ADSI device is capable of receiving data from the public or private computer network including analog voice data and digital data. In the course of using the ADSI device it is often necessary to switch the ADSI device one or more times between the analog and digital modes. Switching is accomplished to the digital mode by transmitting a Customer Premises Equipment Alerting Signal (CAS) that may comprise a short, 80 millisecond burst of one or more tones. A typical CAS dual tone burst consist of 2170 hertz and 2300 hertz. However, the CAS tone is very annoying and many customers complain about the CAS tone. The annoying CAS tone may inhibit both the sales and the use of ADSI devices. Customers complain that the CAS tone hurts their ears and that it is a piercing, sudden, unexpected and fairly loud noise. It is often loud because the tone must be broadcast at a large enough amplitude to reach the ADSI device farthest away from the NAV.
Others have addressed the problem by trying to minimize the occurrence of the CAS tone. That solution was implemented by a computer program stored in the computer telephony apparatus. The computer program was executed by the computer telephony platform to carefully keep track of when the ADSI phone was in the data mode. The softkeys of the ADSI phone can be programmed to put the phone into the data mode, and that avoids receiving a CAS tone. However, there are still instances when a softkey is not effective in switching the ADSI phone into the data mode and the only way to switch the ADSI phone is to play the CAS tone.